I pulled the stat and the ring loked pinched and damaged. I' yhinking it might have been heat or position based damage, but whatever it was the stat wasn't performing right. The new one I swapped in has been rock steady all day, so I figure the stat was the right call.

As for a compression check, I don't think that would be merited given my symptoms. The temperature is, despite the various positions, fairly stable, and if the gasket had failed I would expect more variation as air entered the cooling system, caused local overheating, and got burped. I would also expect my coolant to be overflowing constantly with the 75kpa cap I have in place, and it hasn't dripped a bit. Going the other way I would only be loosing coolant and seeing white exshaust, neither one of which is the case.

Thanks again to everyone for the input, preciate the help.

Best,
rt